Over the past several decades the use of spark-ignited two-stroke cycle (two-cycle, 2-stroke) internal combustion engines has steadily increased. They are presently found in power lawn mowers and other power-operated garden equipment, power chain saws, pumps, electrical generators, marine outboard engines, snowmobiles, motorcycles and the like. These engines may be air-cooled or water-cooled. Two-stroke cycle engines have found limited application as automobile and truck engines. Manufacturers are exploring how to expand this use.
The increasing use of two-stroke cycle engines coupled with increasing severity of the conditions under which they are operated has led to an increased demand for oils to not only adequately lubricate such engines but also provide enhanced performance. Among the problems associated with two-stroke cycle engines are piston ring sticking, piston scuffing, rusting, lubrication related failure of connecting rod and main bearings and general formation of carbon and varnish deposits on the engine's interior surfaces. Piston ring sticking is a particularly serious problem. Ring sticking leads to failure of the sealing function of piston rings. Such sealing failure causes loss of cylinder compression which is particularly damaging in two-stroke cycle engines because many of these engines depend on suction to draw the new fuel charge into the exhausted cylinder. Thus, ring sticking can lead to deterioration of engine performance and unnecessary consumption of fuel and/or lubricant. Other problems associated with two-stroke cycle engines include piston lubricity, scuffing or scoring.
All of the aforementioned problems associated with two-stroke cycle engines must be adequately addressed. Improved performance is continually being sought. The unique problems and techniques associated with the lubrication of two-cycle engines has led to the recognition by those skilled in the art of two-cycle engine lubricants as a distinct lubricant type. See, for example, U.S. Pat. Nos. 3,085,975; 3,004,837; and 3,753,905.
The compositions of the present invention are effective in controlling the aforementioned problems.
While color, per se, is not often a consideration when evaluating performance of a 2-cycle engine lubricant, it may be a consideration for other reasons.
As is well-known, the equipment operator frequently prepares lubricant-fuel blends. A particularly dark colored lubricant or one that imparts a significant color to the lubricant-fuel blend, while not affecting performance, may be considered objectionable. Furthermore, two-stroke cycle oils frequently contain a small amount of dye, to impart a characteristic color to the lubricant-fuel blend. If the color of the lubricant is pronounced, it may mask the color of the dyed fuel or may lead the user to believe that the lubricant-fuel blend has deteriorated.
The lubricating compositions of the instant invention are considerably lighter in color than many commercially available lubricants.
U.S. Pat. No. 4,425,138 relates to amino phenols used in lubricant fuel mixtures for two-cycle engines. U.S. Pat. Nos. 4,663,063 and 4,724,091 issued to Davis relate to a combination of an alkyl phenol and an amino compound in two-cycle engines.
U.S. Pat. Nos. 4,708,809 and 4,740,321 relate to use of alkylated phenols in two-cycle engine lubricants. U.S. Pat. No. 4,231,757 relates to nitrophenol-amine condensates and the use thereof in two cycle oils.
U.S. Pat. No. 5,281,346 relates to two-cycle engine lubricants and fuel-lubricant mixtures comprising metal bis-phenol carboxylates.
Applicants' assignee's co-pending U.S. application Ser. No. 08/061,377 relates to amide and amide-containing derivatives of bis-phenol carboxylic compounds and their use in fuels other than two-cycle fuels.
U.S. Pat. No. 3,954,808 relates to bis (phenol substituted) alkanoic acid compounds as intermediates in preparation of lubricant additives. U.S. Pat. No. 3,966,807 describes amides of bis (phenol substituted) carboxylic acids as lubricating oil additives.